An electroacoustic transducer that mutually converts an electric signal and a sound wave, is incorporated in an electroacoustic transducing device such as a microphone, a headphone, or a speaker. The electroacoustic transducer generates a sound wave corresponding to an electric signal when a diaphragm vibrates based on the electric signal, or generates an electric signal corresponding to a sound wave when a diaphragm vibrates based on the sound wave.
The conversion types of the electroacoustic transducer include a dynamic type using a magnetic field and a capacitor type using an electric field, etc.
A dynamic-type electroacoustic transducer includes a magnetic circuit, a voice coil, a diaphragm, and a housing. The magnetic circuit generates a magnetic field. The voice coil is a conductor disposed in a magnetic field of the magnetic circuit. The voice coil is attached to the diaphragm. The diaphragm generates a sound wave by being vibrated by a driving force generated by flowing an electric signal (electric current) in the voice coil, and generates an electric signal in the voice coil by vibrating together with the voice coil by receiving a sound wave. The diaphragm includes a vibrating portion and an outer rim portion disposed on an outer rim of the vibrating portion. The outer rim portion of the diaphragm is fixed to (held on) an attaching portion of the housing. The housing accommodates the magnetic circuit, the voice coil, and the diaphragm.
As a method of fixing the outer rim portion of the diaphragm to the housing, there is a method using an adhesive agent (for example, refer to Japanese Published Unexamined Patent Application No. H06-178390).
In the method disclosed in Japanese Published Unexamined Patent Application No. H06-178390, the outer rim portion of the diaphragm is adhered to the attaching portion of the housing by an adhesive agent. Normally, an adhesion margin on the attaching portion is narrow, and it is difficult to uniformly apply an appropriate amount of an adhesive agent to the adhesion margin. Therefore, an individual difference in adhesion occurs on the outer rim portion of the diaphragm. That is, for example, when an amount of the adhesive agent is larger than the appropriate amount, the adhesive agent protrudes into the vibrating portion on the inner side of the outer rim portion of the diaphragm and restricts vibration of the vibrating portion. As a result, the frequency characteristics of the electroacoustic transducer deteriorate. In addition, for example, when the amount of the adhesive agent is smaller than the appropriate amount, a gap is formed between the outer rim portion of the diaphragm and the attaching portion of the housing. As a result, when the vibrating portion vibrates, the outer rim portion of the diaphragm collides with the attaching portion of the housing and causes unevenness in frequency response of the electroacoustic transducer (the frequency characteristics deteriorates). Thus, the electroacoustic transducer in which the outer rim portion of the diaphragm and the attaching portion of the housing are fixed by an adhesive agent tends to cause variations in frequency characteristics.
An electroacoustic transducer in which an outer rim portion of a diaphragm is fixed to a housing without using an adhesive agent has been proposed (for example, refer to Japanese Published Unexamined Patent Application No. 2011-18953).
In an electroacoustic transducer disclosed in Japanese Published Unexamined Patent Application No. 2011-18953, an outer rim portion of a diaphragm is mounted on an attaching portion (mounting surface) of a housing (frame), and fixed to the attaching portion of the housing by an elastic-resin-made gasket that is pressed by a lid (baffle). That is, the diaphragm is sandwiched by the gasket and the mounting surface. As a result, without using an adhesive agent, the outer rim portion of the diaphragm is fixed to the mounting surface of the frame.